The publication of G. H. von Fuchs at al., paper entitled “The Rotary Bomb Oxidation Test for Inhibited Turbine Oils,” In the ASTM Bulletin (now the Materials Research and Standards), No. 186, December 1952, pp. 43-46, provided the technical basis for ASTM Method D2272 approved and published in 1964 as a “Rotary Bomb Oxidation Test”. This ASTM Method is now termed the “Rotating Pressure Vessel Oxidation Test” (RPVOT). In this test method, ASTM D2272, a 50-gram sample plus a 5-gram amount of water and a high-purity (99.9%) copper coil are placed in a beaker and loaded into a pressure chamber, sealed and then filled with 99.5% pure oxygen gas at a pressure of 620-kPa, and the entire pressurized chamber Is rotated in an oil bath at 150° C. Initially, the end of test (EOT) was considered to be when the oxygen pressure fell rapidly with oil oxidation. This was called the “break point.” Later, the EOT was set at a 175-kPa (25.4 PSI) pressure drop, which at the time corresponded with the onset of the break point. With more modern fluids, this has not always been found to be the case, and the break point sometimes comes well after a 175-kPa chamber pressure value is reached. Basically, however, that instrument and technique simulated many hours of oil in service in a turbine, for example, by minutes in the RPVOT. The RPVOT is widely used and provides information on the quality and potential longevity of turbine lubricants in service. However, original equipment for D2272 was not without some difficulties in the practice of the original ASTM D2270 method. For example, the following is noted:                It is difficult to maintain an about 100-liter oil bath at 150° C. to bathe multiple, for example, four, test assemblies (which are often rotated through the bottom of the tank where seals are leak-prone under those operating conditions).        Even more important is the fact that running tests in a liquid bath requires that tests in all of the RPVOT units in the bath must be completed before any of them can be disassembled, cleaned and replaced in the bath for another analysis. This retards oxidation testing significantly.        Operator safety Is a concern, especially to avoid being splashed by very hot oil when the heavy (about 10˜15 pounds) pressure-vessel assemblies are loaded or removed after the test.        In addition, the odor and fumes that develop from the bath oil frequently lead to the need for special hoods, associated floor space, and cleaning needs.        
Recently, an instrument was developed to ameliorate or eliminate these problems, which simplified the RPVOT procedure and, in addition, was capable of providing considerable new information and versatility: the Quantum® instrument. Compare, U.S. Pat. No. 7,678,328 B1. The Quantum® instrument entirely avoids using bath oil for heating, simplifies sample loading and retrieval, rotates only the sample beaker instead of the whole pressure chamber and reduces test turn-around time since each sample is run in its own Quantum® instrument. Thus, rather than rotating several complete assemblies simultaneously in an oil bath, only the inner test sample beaker is rotated by magnetic coupling at the bottom of the pressure chamber, which remains stationary. A computer is used to record pressure and temperature data from one to four units. See, e.g., FIG. 1. Since the Quantum® instrument is intended to be, in general, an isothermal reactor, first studies focused on the effects on temperature effects of the oxidation reaction going on in the oil sample during the application of the RPVOT technique. Various observations were reported by T. W. Selby et al., “Studies of the Oxidation Dynamics of Turbine Oils—Initial Data from a New Form of the Rotating Pressure Vessel Oxidation Test,”. This paper by Selby was given at an ASTM Symposium on Oxidation and Testing of Turbine Oils; 5-8 Dec. 2005, in Norfolk, Va. and published in October 2007 in the Journal of ASTM International.
For the first time, the design of the Quantum instrument—with only the sample rotating—permitted inserting a pressure-sealed temperature sensor into the test fluid during test as shown in FIG. 2. When this was done, the ASTM D2272 RPVOT test method was able to record the test fluid. The temperature recording showed a phenomenon never before seen in this test. At the time at which oxidation began to increase rapidly as shown by a relatively precipitous decrease in the oxygen pressure in the pressure chamber, some oils showed an exotherm in temperature in which the sample temperature would rise as shown in FIG. 3 That the test fluid oxidation rate could produce such a response was an important new finding. It provided a way of contrasting oxidation inhibitors and the oxidation response of test oils. The degree of temperature increase was found to range from a few tenths of a degree to well over +15° C., in cases perhaps to +30° C. or so, and this information on the variation of oxidation reactivity is, in itself, informative about inhibitors.
Difficulties with previous endeavors in the field include that repeatability, accuracy and precision are not as good as one would hope in order to obtain the best data so necessary for a more complete understanding of the sample under test. This, in turn, can lead to less in the way of advancement, for example, in the world of lubricants, than would allow with better data. It would be desirable to improve upon the art as well as to provide the art an alternative.